Wrapping machine

ABSTRACT

A method and an apparatus ( 10 ) for wrapping a bundle on 5 of the 6 faces thereof comprises gripping fingers ( 44 ) for holding a sheath (S) from opposed lateral sides of the bundle while folding members ( 62, 64 ) pivot into the sheath to tuck in inner creases along the sides of the bundle also thereby forming two-ply outer creases. The two-ply outer creases are brought down against the inner creases by the gripping fingers ( 44 ) and a sealing unit ( 40 ) is presses against the sides of the bundle to seal the so formed three-ply folds.

TECHNICAL FIELD

The application relates generally to an apparatus and a method forwrapping goods, such as bundles, with sheathing materials.

BACKGROUND OF THE ART

There is a need for a new apparatus and method for providing effectiveand convenient wrapping or sheathing of rigid wood products, such aswood joists with sheathing materials or the like.

SUMMARY

In one aspect, there is provided a method for wrapping a bundle into asheath, the method comprising: drawing the sheath in front of thebundle, holding the sheath against a front face of the bundle, drawingthe sheath over a top surface of the bundle while the sheath is beingheld at the front of the bundle, creating a three-ply fold in the sheathon each opposed lateral sides of a front end portion of the bundle,sealing the three-ply folds, drawing the sheath over a rear face of thebundle, holding the sheath against the rear face of the bundle, creatinga three-ply fold in the sheath on each opposed lateral sides of a rearend portion of the bundle, and sealing the three-ply folds.

In accordance with a further aspect of the present invention, there isprovided a method of bagging a bundle into a sheath having a bottom openface comprising covering the bundle with the sheath, creating a pleat ateach corner of the sheath, each pleat being made by doubling the sheathover on itself to form a section of three thicknesses including an innercrease along a side of the bundle and a two-ply outer crease having twosuperposed sheath layers, and joining the two-ply outer crease of eachpleat to the associated inner crease.

In accordance with still further aspect, there is provided an apparatusfor wrapping a bundle, comprising a conveyor for carrying the bundlethrough the apparatus, a sheath dispensing unit for covering a topsurface and the lateral sides of the bundle with a sheath, first andsecond pairs of gripping fingers for holding the sheath from opposedlateral sides of the bundle, folding members disposed on opposed lateralside of the conveyor to tuck in the sheath along the sides of the bundleat each end of the bundle while the sheath is held by said grippingfingers, thereby forming pleats at each corner of the sheath, each pleatcomprising an inner crease lying against an underlying side surface ofthe bundle and a two-ply outer crease held by the gripping members, thefirst and second pairs of gripping members being movable to draw thetwo-ply outer creases over corresponding inner creases, and a joiningunit engageable with the sheath to join the two-ply outer crease to theunderlying inner crease at each pleat.

Further details of these and other aspects of the present invention willbe apparent from the detailed description and figures included below.

DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompanying figures, in which:

FIG. 1 a is a front perspective view of an embodiment of a wrappingmachine;

FIG. 1 b is a top perspective view of the wrapping machine shown in FIG.1 a;

FIG. 2 is a simplified front perspective view of the wrapping machineillustrating the relative positions of various components of the machinebefore the wrapping operation be initiated, some of the components beingomitted for clarity purposes;

FIG. 3 is a simplified front perspective view of the wrapping machineillustrating how the sheath is first drawn in front of the bundle to besheathed;

FIG. 4 is a simplified front perspective view of the wrapping machineillustrating how the sheath is held and maintained against the frontface of the bundle;

FIG. 5 is a simplified front perspective view of the wrapping machineillustrating how the sheath is pulled rearwardly over the top face ofthe bundle;

FIG. 6 is a simplified front perspective view of the wrapping machineillustrating how the front sides of the sheath are gripped to permit thesame to be subsequently folded over against the lateral sides of thefront end portion of the bundle;

FIG. 7 is a simplified front perspective view of the wrapping machineillustrating the folding operation of the front corners of the sheathagainst the front sides of the bundle;

FIG. 8 is a simplified front perspective view of the wrapping machineillustrating the sealing of the folded front corners of the sheath;

FIG. 9 is a simplified front perspective view of the wrapping machineillustrating a partly wrapped bundle in the process of being move in theforward direction in order to bring the rear end of the bundle inalignment with the folding and sealing components of the machine;

FIG. 10 is a simplified front perspective view of the wrapping machineillustrating the lowering of a weighting component and guiding rods ontop of the sheath in preparation of the subsequent cutting, folding andsealing operations at the rear end of the sheath;

FIG. 11 is a simplified front perspective view of the wrapping machineillustrating the sheath covering the rear face of the bundle afterhaving been cut from the remainder of the roll of sheath;

FIG. 12 is a simplified front perspective view of the wrapping machineillustrating the formation of the folds against the sides of the rearend of the bundle;

FIG. 13 is a simplified front perspective view of the wrapping machineillustrating the sealing of the folded rear corners of the sheath; and

FIG. 14 is a simplified front perspective view of the wrapping machineillustrating the withdrawal of the folding and sealing component of theapparatus to permit the exit of the bundle once the wrapping operationhas been completed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now referring to the drawings, and in particular to FIGS. 1 a and 1 b, awrapping apparatus 10 suited for sheathing, bagging or wrapping bundlesB of varying height and length with a sheath S will be described. Theapparatus 10 is suited for wrapping bundles on 5 of the 6 faces thereof(i.e. the four lateral sides and the top face) leaving the bottom faceuncovered. The apparatus 10 is particularly suited for wrapping bundlesB having non-uniform or uneven lateral sides. In the illustratedexample, the bundle is composed of a number of elongated I-shaped woodbeams or joists. The I-shaped cross-section of the beams provides forelongated recessed lateral surfaces along the opposed longitudinal sidesof the bundle. Wrapping that type of bundles is challenging because thelateral sides of the bundles do not provide uniform abutting surfaces topermit sealing of the sheath on the bundle.

The apparatus 10 generally comprises a motorized conveyor 12 fortransporting successive bundles B through the apparatus 10. A pair ofsiderails 14 extends lengthwise along opposed longitudinal sides of theconveyor 12. A carrier 16 is mounted on the siderails 14 for axialforward and backward movement relative to the bundle B on the conveyor12, as depicted by arrow 15 in FIG. 1 b. An actuator 18, such areversible electric motor, a pneumatic or hydraulic cylinderarrangement, is provided for displacing the carrier 16 back and forthalong the siderails 14. A sheath dispensing unit including a roll ofsheath material carried on an overhead supply reel 20 and two pairs ofvertically aligned motorized indexing rollers 22 are mounted to thecarrier 16. The supply reel 20 is supported above the conveyor 12 forrotation about a horizontal axis transversal to the conveyor 12, therebyproviding for the dispensing of the sheath S in the longitudinal/feedingdirection of the conveyor 12. As shown in FIG. 1 a, the sheath S isprovided in the form of a film or an elongated web of flexible,stretchable, resilient plastic material, rolled on the supply reel 20.It is understood that other types of bagging material could be used. Forinstance, the sheathing material could be provided as a pre-formed baghaving one open end. The first and second pairs of indexing rollers 22are mounted on a support 24 which is, in turn, mounted for verticalmovement along two upstanding posts 28 forming part of the carrier 16.Actuators, such as pneumatic or hydraulic cylinders, are provided forselectively raising or lowering the indexing roller assembly along theposts 28. A pair of guide rods or rollers 30 are also carried by thesupport 24 in front of the indexing rollers 22 for engaging the sheath Swhile the same is being drawn over the top surface of the bundle B.Actuators 32, such as pneumatic or hydraulic cylinders, are provided forselectively raising or lowering the guide rollers 30 relative to theindexing rollers 22. The guide rollers 30 can be mounted at the distalend of respective arms pivotally mounted on each side of the support 24.

As can be appreciated from FIG. 1 a, the sheath S is directed from thesupply reel 20 to the first and second pairs of indexing rollers 22.Each pair of rollers 22 can be opened for receiving the sheath Stherebetween and then closed against the sheath S for drawing the samefrom the reel 20. The first and second pairs of indexing rollers 22 canbe driven at different speeds in order to pre-stretch the sheath S,thereby subsequently facilitating the full stretching thereof in thewrapping apparatus 10. Additional set of pre-stretching rollers drivenat increased speed from one set to the next could be provided forpre-stretching the sheath S.

A bottom transversal rail 32 is provided at the front end of theapparatus 10. First and second pairs of elongated gripping fingers 34are provided at opposed ends of the bottom transversal rail 32 forselectively holding the sheath S on opposed longitudinal sides of thebundle B. The first and second pairs of gripping fingers 34 are mountedat the upper end of respective vertically disposed Z-shaped arms 36. TheZ-shaped arms 34 are linearly displaceable along opposed end portions ofthe rail 32 toward and away from each other between a retracted/outwardposition (FIG. 1 a) and an operational/inward position (FIG. 4). Anactuator 38, such as a pneumatic or hydraulic cylinder, is provided toreciprocate each Z-shaped arm 36 and the associated pair of grippingfingers 34 along the bottom transversal rail 32. Actuators are alsoprovided to selectively open and close each pair of gripping fingers 34in a horizontal plane.

First and second heat sealing members 40 are facing each other fromopposed sides of the apparatus 10 for sealing the corners of the sheathS after the same have been folded over on opposed sides of the bundle B,as will be seen hereinafter. The sealing members 40 are reciprocablealong transversal rail segments 42 mounted at the front end portion ofthe longitudinal side rails 14 behind the gripping fingers 34. Actuators(not shown) are provided for displacing the sealing members 40 from anoutwardly retracted position (FIGS. 1 a and 1 b) to an inwardly extendedposition (FIG. 8) in a direction transversal to the longitudinal/feedingdirection of the conveyor 12.

First and second pairs of pivotable gripping fingers 44 are facing eachother from opposed longitudinal sides of the apparatus 10. The first andsecond pairs of pivotable gripping fingers 44 are mounted forreciprocating movement along respective pivotable ramps 46. Actuators45, such as pneumatic or hydraulic cylinders, are provided fordisplacing the pairs of fingers 44 along the ramps 46. The ramps 46 arepivotally mounted to a rear facing side of rail segments 42 forupward/downward pivotal movements between a collapsed position (FIG. 1a) to clear the passage for the indexing rollers 22 and a raisedposition (FIG. 1 b) in which the ramps 46 are inclined at 45 degreesfrom the horizontal plane of the apparatus 10. Actuators, such aspneumatic or hydraulic cylinders, are provided for raising and loweringthe pivotable ramps 46. Referring to FIGS. 6 and 7, it can be seen thateach pair of fingers 44 are also pivotable or swignable from ahorizontally extending position (FIG. 6) to a vertically upwardlyextending position (FIG. 7). Suitable actuators are provided forswinging the fingers 44 between their horizontal and vertical positions.The pivotable fingers 44 open and close in a vertical plane that is in aplane perpendicular to the opening and closing plane of the abovedescribed elongated fingers 34. Suitable actuators are provided foropening and closing the fingers 44.

As best seen in FIG. 1 b, a pair of upstanding posts 48 are mounted forlinear back and forth movements on front rail segments 50 provided atthe front of the siderails 14. Actuators 52, such as pneumatic orhydraulic cylinders, are provided for reciprocating the posts 48 alongthe axially extending rail segments 50. A transversal weighting member54 is mounted at opposed ends thereof to the posts 48 for upward anddownward movement along the upper end portion of the posts 48. Actuators56, such as pneumatic or hydraulic actuators, are provided for raisingand lowering the weighting member 54.

As shown in FIG. 1 a, a pair of anvil members 58 may be mounted atopposed ends of a bottom shaft 60 and are spaced by a distancesufficient to accommodate a bundle of predetermined width therebetween.The anvil members 58 are pivotable to an upstanding position in whichthe anvil members 58 lie vertically between the sheath S and theadjacent lateral surface of the bundle B (see FIGS. 5 to 8) in order tooffer uniform abutting surfaces to the sealing members 40 during thesealing operation of the folded corners of the sheath S. In theillustrated example, the anvil members 58 palliate for the non-uniformlateral surfaces resulting from the I-shaped cross-section of the woodjoists composing the bundle to be wrapped. Each anvil member 58 providesa flat and uniform surface on the inner side of the package againstwhich the associated sealing member 40 can be pressed in order to obtaina strong and uniform seal in the sheath S. The use of the anvil members58 is particularly optional when the items to be wrapped already have auniform lateral surface against which the sealing members 40 could bepressed to form a seal in the sheath S. As shown in FIG. 14, each anvilmember 58 can be pivoted forwardly downwardly to a rest position inwhich the anvil member lies horizontally below the bundle that has justbeen wrapped, thereby allowing the discharge of the wrapped bundle fromthe apparatus 10. The anvil members 58 rotate together with the bottomshaft 60. A reversible electric motor 65 can be provided for rotatingthe anvil members 58 together with the bottom shaft 60.

As shown in FIG. 1 a, a pair of front and a pair of back sheath foldingmembers 62 and 64 are also mounted to the opposed ends of the bottomtransversal shaft 60 for independent pivotal movement thereabout. Eachsheath folding member 62, 64 has its own actuator 66, 68. In theillustrated examples, the actuators 66 and 68 are provided in the formof pneumatic cylinders. The actuators 66 are operable to pivot the frontfolding members 62 from a forwardly horizontally extending position(FIG. 1 a) to an upstanding position (FIG. 7) for folding the corners ofthe sheath S at the front end of the bundle. Likewise, the actuators 68are operable to pivot the rear sheath folding members 64 from arearwardly horizontally extending position (see folding member 64 on theleft hand side of FIG. 1 a) to an upstanding position (FIG. 12) forfolding the corners of the sheath S at the rear end of the bundle B. Therear folding members 64 are further pivotable forwardly from theirfunctional upstanding position together with the bottom shaft 60 and theanvil members 58 to a forwardly horizontally extending position (seefolding member 64 on the right hand side of FIG. 1 b and FIG. 14).Bushings or the like are provided between the shaft 60 and the frontfolding members 62 to allow the shaft 60 to rotate without driving thefront folding member 62 in rotation and vice versa.

Each folding members 62,64 can be provided in the form of a two-piecepart comprising a stem 62 a, 64 a pivotally mounted to the shaft 60 anda freely articulated arm 62 b, 64 b pivotally mounted to a distal endportion of the stem 62 a, 64 a. The operation and construction of thefront and rear folding members 62, 64 are similar and, thus, will onlybe described in connection with one of the front folding members 62. Asbest seen in FIG. 6, when not in use, the articulated arm 62 b lies overone side of the stem 62 a. The articulated arm 62 b and the stem 62 aare partially longitudinally offset so that a distal end portion of thearticulated arm 62 b projects beyond the underlying stem 62 a above thepivot between the arm 62 b and the stem 62 a, thereby providing a leveragainst which a force can be applied to pivot the arm 62 b relative tothe stem 62 a. When the folding member 62 is pivoted to its upstandingfunctional position, as depicted by arrow 70 in FIG. 7, the articulatedarm 62 b is caused to pivot in the opposite direction, as shown by arrow72, relative to the stem 62 a under the force exerted by the sheath S onthe distal upper end portion (i.e. the lever) of the arm 62 b inreaction to the advancement of the folding member 62 in the sheath. Thepivotal movement of the articulated arm 62 b allows to roughly forming a45 degrees fold in the sheaths S, as shown in FIG. 7.

As shown in FIGS. 1 a, 1 b, 2 and 4, a set of front heel members 74 aremounted on a transversal shaft 76 provided at the front discharged endof the conveyor 12. The front heel members 74 are jointly pivotablebetween a rest position (see FIGS. 1 a and 2) in which the heel members74 extend in a horizontal plane slightly below a top surface of theconveyor 12 for allowing the passage of the bundle thereover, and araised position (FIG. 4) for retaining the sheath S against the frontface of the bundle B. An actuator (not shown) is provided for pivotingthe front heel members 74 between their lowered and raised positions.

Likewise, as shown in FIG. 14, a set of back heel members 78 are mountedon a transversal shaft 80 provided at the inlet end of the machine 10.The back heel members 78 are pivotable between a lowered position (FIG.11) for allowing the passage of the bundle B thereover and a raisedposition in which the back heel members 78 maintain the sheath S againstthe back face of the bundle B.

A cutting unit (not shown) is provided at the inlet end of the machine10 for transversally cutting the sheath S at the back of the bundle B.

The operation of the machine and the various steps of the bundlewrapping process will now be described with reference to FIGS. 2 to 14.It is noted that some of the structural elements of the machine 10 havebeen omitted from FIGS. 2 to 14 in order to better illustrate thevarious sequences of the wrapping operation. For instance, only theright hand side parts are shown, the corresponding left hand side partshaving the same mode of operation.

FIG. 2 shows the initial position of the parts of the machine. The frontand back heel members 74 and 78 are lowered in order not to interferewith the advancement of the bundle B on the conveyor 12. The carrier 16,which supports the roll of sheath S and the indexing rollers 22, standsin its upstream most position relative to a feeding direction of thebundle B through the machine 10. The height of the indexing rollers 22and guide rollers 30 on the posts 28 of the carrier 16 is adjustedaccording to the height of the bundle B to be wrapped. The pivotableramps 46 are lowered to clear the passage of the indexing rollers 22carried by the carrier 16. The elongated gripping fingers 34 and thesealing units 40 are retracted laterally outward to their restpositions. The anvil members 58 are raised in their upstanding positionfor receiving the bundle B therebetween. The front and back sheathfolding members 62 and 64 are lowered to their rest positions. Theweighting member 54 assumes its raised position and the posts 48carrying the weighting member 54 stand in their upstream most positionon the front rail segments 50 of the siderails 14.

First, a length of sheath S is unrolled from the supply reel 20 andengaged between the motorized indexing rollers 22 and the bundle B isadvanced on the conveyor 12 between the raised anvil members 58 to aposition wherein the front face of the bundle B is disposed slightlydownstream of the anvil members 58, as shown in FIG. 2. The first andsecond pairs of motorized rollers 22 are driven at different speeds topre-stretch the sheath S and draw the same in front of the bundle B, asshown by arrows 81 in FIG. 3.

As shown by arrows 83 in FIG. 4, the elongated gripping fingers 34 aredisplaced transversally inwardly along the bottom rail 32 towards thebundle B to grip the sheath S. At the same time, the front heel members74 are pivoted upwardly against the front face of the bundle B to holdthe sheath S thereagainst.

The carrier 16 supporting the supply reel 20 and the indexing rollers 22is then displaced backward along the siderails 14 to draw a length ofsheath S over the top surface of the bundle B, as represented by arrows85 in FIG. 5. The guide rollers 30 are lowered to press the sheath Sagainst the top surface of the bundle B while the carrier 16 is beingdisplaced rearwardly. The carrier 16 is displaced to a position which isupstream from the pivotable ramps 46 relative to a feeding direction ofthe bundle through the machine.

As depicted by arrow 87 in FIG. 6, the ramps 46 are then pivotedupwardly to their operational position. In this position, the ramps 46have a 45 degrees inclination. This allows the gripping fingers 44 togrip the sides of the sheath S on bundles of different height. Asrepresented by arrow 89, the gripping fingers 44 are displaceddownwardly along the inclined ramps 46 to an intermediate position wherethe gripping fingers 44 grab the sheath S on each longitudinal lateralsides of the bundle B.

Once the small gripping fingers 44 firmly holds the sheath S, theelongated gripping fingers 34 open and retract to their rest position,as represented by arrows 91 in FIG. 7. The front folding members 62 arethen pivoted upwardly as depicted by arrow 70 to create a pleat at eachside of the front end portion of the bundle. The pleat is defined by a45 degree fold in the sheath made by doubling sheath over on itself toform a section of three thicknesses or layers including an inner creasealong the side of the bundle and an outer crease having two superposedsheath layers, As depicted by arrow 93, the gripping fingers 44 thencontinue their stroke down the inclined ramp 46 and swing to theirvertical orientation as shown by arrow 95, thereby pulling the doublelayer outer crease of the sheath S over the inner crease with the innerlayer of the double layer outer crease lying against the outwardlyfacing surface of the inner crease previously tucked in by the frontfolding fingers 62. This provides for a three-layer folded corner oneach side of the front end portion of the bundle B.

As shown in FIG. 8, the sealing members 40 are then displacedtransversally inwardly against the opposed lateral longitudinal sides ofthe bundle B to seal the three-layer folded corners of the sheath S. Theanvil members 58 on the inner side of the sheath S provides a uniformresting or backing surface against which the sealing members 40 can bepressed for sealing the front folded corner of the sheath S. Thethree-layer folded corners on opposed sides of the bundle are firmlyheld between the anvil members 58 and the sealing members 40 during theheat sealing process, there by providing for sturdy front seam at eachside of the bundle B.

After the sealing operation, the gripping fingers 44 open and movefurther down the ramps 46 out of engagement from the sheath S. Thegripping fingers 44 then swing back to their original horizontallyextending position and move up the ramps 46 to their retracted position,as depicted by arrow 97 in FIG. 9. The sealing members 40 also retractto their rest position, as depicted by arrows 99. The conveyor 12 isthen powered to abut the front face of the bundle B firmly against thefront heel members 74. The carrier 16 supporting the roll of sheath isdisplaced backward to further taut the sheath S over the front endportion of the bundle B. Then, the front heel members 74 are pivotedforwardly to their horizontally lying position and the conveyor 12 isoperated to displace the bundle forwardly together with the carrier 16supporting the supply reel 20 and the indexing rollers 22. The frontfolding members 62 are pivoted back to their rest position, as depictedby the arrow 101. The conveyor 12 and the carrier 16 are synchronized toadvance the bundle B, the supply reel 20 and the indexing rollers 22 atthe same speed. The indexing rollers 22 are operated to unroll a lengtha sheath S in accordance with the length of the bundle B.

As depicted by arrows 105 in FIG. 10, the guide rollers 30 are loweredon top of the bundle B for positioning the sheath S for the grippingfingers 44. The conveyor 12 is stopped to immobilize the rear endportion of the bundle B in line with the anvil members 58. Then, asshown by arrows 107, the weighting member 54 is lowered on top of thebundle B to maintain the tension in the sheath S over the bundle B. Thegripping fingers 44 are moved down the ramps 46 for gripping the sheathS, as represented by arrow 109. A cutter (not shown) is then operated totransversally cut the sheath at the rear of the bundle B.

After the sheath has been cut as shown in FIG. 11, the gripping fingers44, move up a predetermined distance along the ramps 46 for tensioningthe sheath S on the bundle B. Thereafter, the rear heel members 78 (seeFIG. 11) are pivoted upwardly to maintain the rear flap of the sheathagainst the rear face of the bundle B. The rear folding members 64 arepivoted to their upward position to create the folds in the sheath S onboth opposed lateral rear sides of the bundle B (see arrow 111 in FIG.12). The gripping fingers 44 are displaced down the ramps 46 to anintermediate position and swung to their vertical orientation (seearrows 113 and 115 respectively) such as to pull the double-layer outercrease downwardly over the inner crease formed in the sheath S by therear folding members 64.

As depicted by arrows 117, the sealing members 40 are displacedtransversally inwardly against the anvil members 58 disposed between thesheath S and the bundle B. The three-layer folded sheath corners pressedbetween the anvil members 58 and the sealing members 40 are sealed,thereby forming the rear end of the sheath envelope about the bundle.

Finally, as shown in FIG. 14, the sealing members 40 and the grippingfingers 44 are retracted, the rear folding members 64 are pivotedforwardly together with the anvil members 58 to a substantiallyhorizontally lying position and the weighting member 54 is raised fromthe bundle B. The conveyor 12 can then be operated to discharge thebundle B that has just been wrapped.

Once the wrapping cycle has been completed, the various parts of themachine are displaced back to their original position for receiving thenext bundle to be wrapped.

The above description is meant to be exemplary only, and one skilled inthe art will recognize that changes may be made to the embodimentsdescribed without departing from the scope of the invention disclosed.For example, the anvil members could for instance be omitted when thelongitudinal lateral sides of the bundle are flat or free from any voidsor recesses. The front and rear folding members 62 and 64 could have aone-piece construction. For example, they could be provided in the formof one-piece boomerang-shaped urethane members. The 45 degrees ramps 46could be fixed. The indexing and the supply reel could move upwardly toprovide the required clearance. Also the three-ply fold at the cornersof the sheath could be secured by any suitable means (i.e. heat sealingbeing only one possible way of holding the folds in place). Still othermodifications which fall within the scope of the present invention willbe apparent to those skilled in the art, in light of a review of thisdisclosure, and such modifications are intended to fall within theappended claims.

1. A method for wrapping a bundle into a sheath, the method comprising:drawing the sheath in front of the bundle, holding the sheath against afront face of the bundle, drawing the sheath over a top surface of thebundle while the sheath is being held at the front of the bundle,creating a three-ply fold in the sheath on each opposed lateral sides ofa front end portion of the bundle, fastening the three-ply folds inplace, drawing the sheath over a rear face of the bundle, holding thesheath against the rear face of the bundle, creating a three-ply fold inthe sheath on each opposed lateral sides of a rear end portion of thebundle, and fastening the three-ply folds in place.
 2. The methoddefined in claim 1, wherein the fastening steps comprise placing ananvil member between the sheath and the bundle and pressing thethree-ply folds between the anvil member and a heat sealing member. 3.The method defined in claim 1, wherein creating a three-ply foldcomprises moving a folding member on one side of the bundle into alaterally held portion of the sheath, the engagement of the foldingmember in the sheath forming a fold in the sheath, the fold defining aninner crease lying against an underlying side surface of the bundle anda two-ply outer crease in a remaining portion of the laterally heldportion of the sheath, and drawing the two-ply outer crease over theinner crease, thereby forming a three-ply fold.
 4. The method defined inclaim 1, wherein creating a three-ply fold comprises holding a sideportion of the sheath so as to create a foldable flap extendinglaterally outwardly from one end of the bundle, moving a folding memberin the foldable flap to tuck in a first portion of the flap against oneside of the bundle, thereby forming an inner crease, and pulling aremaining portion of the foldable flap over the first portion of thesheath.
 5. The method defined in claim 3, wherein the folding member hasa stem and a freely articulated arm pivotally mounted to a distal endpotion of the stem, the freely articulated arm having a lever portionextending beyond the stem portion, and wherein continued advancement ofthe folding member in the laterally held portion of the sheath causesthe articulated member to pivot relative to the stem under the forcetransmitted from the sheath to the lever portion of the articulated arm,thereby creating a fold line in the sheath.
 6. The method defined inclaim 4, wherein holding a side portion of the sheath comprises moving apair of gripping fingers along a ramp having a 45 degrees inclination toan elevation corresponding generally to a top surface of the bundle, andthen gripping the sheath with the gripping fingers.
 7. The methoddefined in claim 6, wherein pulling a remaining portion of the foldableflap over the first portion of the sheath comprises moving the grippingfingers down the ramp and pivoting the gripping fingers from ahorizontal orientation to a vertical orientation.
 8. A method of bagginga bundle into a sheath having a bottom open face comprising covering thebundle with the sheath, creating a pleat at each corner of the sheath,each pleat being made by doubling the sheath over on itself to form asection of three thicknesses including an inner crease along a side ofthe bundle and a two-ply outer crease having two superposed sheathlayers, and for each pleat, joining the two-ply outer crease to theinner crease.
 9. The method defined in claim 8, wherein creating a pleatcomprises moving a folding member on each side of the bundle into alaterally held portion of the sheath, the engagement of the foldingmember in the sheath forming a fold in the sheath, the fold defining theinner crease and the two-ply outer crease, and drawing the two-ply outercrease over the inner crease.
 10. The method defined in claim 9, whereinthe laterally held portion of the sheath is held by a pair of grippingfingers movable along a ramp having a 45 degrees inclination.
 11. Themethod defined in claim 10, wherein drawing the two-ply outer creaseover the inner crease comprises moving the gripping fingers down theramp and pivoting the gripping fingers from a horizontal orientation toa vertical orientation.
 12. An apparatus for wrapping a bundle,comprising a conveyor for carrying the bundle through the apparatus, asheath dispensing unit for covering a top surface and the lateral sidesof the bundle with a sheath, first and second pairs of gripping fingersfor holding the sheath from opposed lateral sides of the bundle, foldingmembers disposed on opposed lateral side of the conveyor to tuck in thesheath along the sides of the bundle at each end of the bundle while thesheath is held by said gripping fingers, thereby forming pleats at eachcorner of the sheath, each pleat comprising an inner crease lyingagainst an underlying side surface of the bundle and a two-ply outercrease held by the gripping members, the first and second pairs ofgripping members being movable to draw the two-ply outer creases overcorresponding inner creases, and a joining unit engageable with thesheath to join the two-ply outer crease to the underlying inner creaseat each pleat.
 13. The apparatus defined in claim 12, wherein the sheathdispensing unit comprises an overhead supply reel mounted on a carrieraxially displaceable back and forth relative to a feeding direction ofthe conveyor, and indexing rollers mounted to a support which is in turnmounted to the carrier for up and down movement with respect thereto.14. The apparatus defined in claim 12, wherein the joining unitcomprises first and second heat sealing members facing each other fromopposed sides of the conveyor, the sealing members being movable towardsand away from each other along an axis transversal to the conveyor. 15.The apparatus defined in claim 12, wherein the first and second pairs ofgripping members are reciprocable along respective ramps, the rampsbeing oriented transversally to the conveyor and having an inclinationof about 45 degrees.
 16. The apparatus defined in claim 13, wherein thefirst and second pairs of gripping members are reciprocable alongrespective ramps, the ramps being oriented transversally to the conveyorand having an inclination of about 45 degrees when the gripping fingersare displaced to a sheath grabbing position, and wherein the ramps arepivotable to a collapsed position to clear the passage of the indexingrollers.
 17. The apparatus defined in claim 12, wherein each pair ofgripping fingers is pivotable from a horizontally extending position toa vertically extending position.
 18. The apparatus defined in claim 14,further comprising a pair of anvil members mounted on opposed sides ofthe conveyor, the anvil members being displaceable between a collapsedposition to an upstanding position in which the anvil members lievertically between the sheath and an adjacent surface of the bundle inalignment with the first and second heat sealing members, the anvilmembers offering substantially uniform bearing surfaces against whichthe first and second heat sealing members can be pressed during thesealing operation.
 19. The apparatus defined in claim 13, furthercomprising front and rear heel members pivotable between a collapsedposition for clearing the passage of the bundle on the conveyor and araised position for respectively retaining the sheath against the frontand rear faces of the bundle while the carrier is displaced relative tothe bundle.
 20. The apparatus defined in claim 12, wherein the foldingmembers are pivotable about an axis generally transversal to theconveyor for movement between an idle position in which the foldingmembers lie in a generally horizontal plane and an upstanding positionfor tucking in the sheath along the sides of the bundle.
 21. Theapparatus defined in claim 12, wherein each of the folding members has astem and a freely articulated arm pivotally mounted to a distal endportion of the stem, the articulated arm and the stem are partiallylongitudinally offset, the articulated arm having an end portionextending beyond the distal end portion of the stem to provide a leverfor automatically causing the arm to pivot relative to the stem when aforce is applied on the lever.